Interpretive Summary: The projected loss of methyl bromide as a soil fumigant in 2001 because of environmental concerns has underscored the need for reliable, environmentally and economically acceptable alternative methods for soil disinfestation. Agriculture has depended heavily on the fumigant, methyl bromide, for soil fumigation and quarantine treatments for the exportation of fruit and vegetables. In looking for alternatives to methyl bromide, i is difficult to evaluate the effectiveness of soil fumigants applied to planting beds or greenhouse containers to control pathogens, insects, and weed seeds. Researchers at the USDA, ARS, Appalachian Fruit Research Station, Kearneysville, WV, and Biocontrol of Plant Disease Laboratory, Beltsville, MD, have devised a rapid screening method to test the effectiveness of potential alternatives to methyl bromide for the fumigation of soil. By using this method, a number of natural plant-derived volatiles have been found to be effective fumigants against number of common fungi in the soil which attack the roots of plants. It is anticipated that this research will lead to the discovery of natural compounds which can be used as alternatives to methyl bromide and which will be safer to man and the environment.

Technical Abstract:
An apparatus was developed for the rapid evaluation of soil fumigants in a controlled manner using small volumes of soil and a simple assay procedure. The apparatus consisted of a manifold to which six canisters containing a sandy loam soil adjusted to 100 kPa infested either with conidia of Fusarium oxysporum or Trichoderma harzianum; sclerotia of Sclerotinia minor; ascospores of Talaromyces flavus; or beet seed colonized with Phytium aphanidermatum or Rhizoctonia solani. Using nitrogen (N) as a carrier gas, either N or N plus benzaldehyde or acetic acid was passed through the soil for 24, 48, or 72 h. At all three exposure times, benzaldehyde + N reduced viability of R. solani and S. minor, and reduced populations of P. aphanidermatum and T. harzianum. Populations of F. oxysporum were reduced after 48 and 72 h of exposure to benzaldehyde, whereas populations of T. flavus were reduced only after 72 h exposure. Similarly, at all three exposure times, acetic acid + N reduced viability of R. solani and S. minor, and populations of P. aphanidermatum, F. oxysporum, T. harzianum, and T. flavus.